Sensory hypersensitivity is commonly seen in FXS patients and the FXS mouse model - the Fmr1 knockout (KO). Recent data suggests that this abnormality stems from hyperexcitability in sensory circuits. We have established that cortical microcircuits are hyperexcitable in the Fmr1 KO mouse model, and that sensory responses are enhanced in Fmr1 KO mice and FXS patients. Thus, investigation of sensory sensitivities is clinically relevant, but perhaps more important is the promise of sensory system studies to advance understanding of the mechanisms and consequences of hyperexcitabiity in neocortical circuitry that could represent a primary pathophysiological factor impacting the development of a wide range of perceptual, cognitive, and language skills in FXS. Further, we have identified biochemical signaling mechanisms that may underlie hyperexcitability involving processes that we and others have uncovered that can be examined in detail in KO mouse models and tested in FXS patients to develop a foundation for novel therapeutic development. The striking consistency of findings across levels of investigation and species offers an unprecedented opportunity to investigate mechanisms of brain dysfunction in a mouse disease model and translate it directly to patients - a multidisciplinary mission that is ideal for a Center environment. Our Center is organized to pursue precisely this aim with a tightly integrated and highly novel scientific program of translational research. Project 1 (Huber/Gibson; UTSW; co-PIs) will determine the cellular, molecular and synaptic mechanisms of auditory neocortical dysfunction using in vitro brain slices in FXS mouse models. Project 2 (Razak/Etheil/Binder; UCR; co-PIs) will study auditory sensory processing deficits in vivo in FXS mouse models, test mechanisms, and examine developmental and structural correlates of these deficits. Project 3 (Sweeney/Byerly, UTSW, co-PIs) will investigate auditory cortical processing deficits using novel neurophysiological strategies in individuals with FXS. All Projects will examine candidate mechanisms of sensory hyperexcitability with an acute pharmacological probe strategy to test mechanisms of interest in parallel studies of mice and patients